500 efi versus 525efi

[Partycattin]

Rookie question;
What is the difference in these two motors? Different block?

[Havasu_Dreamin]

525 has more HP and also has closed cooling...

[Dkahnjob]

Rookie question;
What is the difference in these two motors? Different block?
They are both 502 blocks, the difference is that the 525 has Edelbrock aluminum heads and closed cooling, that bumps the hp from 500 to 525. Otherwise basically the same engine. I think they may have upgraded the valve springs as well.
When I spoke to the Mercruiser rep at a show he told me when I do the valve spring service on my 500's to have the 525 valve springs installed.

[acatitude]

525 has more HP and also has closed cooling...
more horsepower...... just remember boobs and horsepower are the same............ if some is good , more is better:D :D

[BadKachina]

Rookie question;
What is the difference in these two motors? Different block?
500efi had 470 hp. Cast iron heads, mefi 3 or 4, CMI e-top headers, smaller cam.
525's are about 540 hp. Alum heads, pcm 555 (way more advanced), Crane 741 series cam, sport tube headers, closed cooling.
I've seen valve train issues with both motors.

[Not So Fast]

more horsepower...... just remember boobs and horsepower are the same............ if some is good , more is better:D :D
Great analogy:D Sort of like big screen TV's
Dont forget the PRICE difference!!!:eek:
I was told the earlier HP 500's were the ones with valve spring problems but that was not the case in later ones, and I trust my mechanic completely;) :D
I made the switch from a 496 HO to an HP500 and couldnt be happier, top speed was what we expected in terms of the increase but mid range and acceleration was the biggest factor. Looks also are MUCHO BETTER, not knocking the HO but the blue motor just looks so much better, that is if you are into looks:rolleyes: And any motor can have problems, that goes without saying right, I've had my share:( NSF

[ULTRA26 # 1]

I have heard that the 525, uses a 502/502 crate motor base, with valve upgrades, a different cam, Merc EFI and Ignition.

[Keith E. Sayre]

Lots of good info here. Although Merc doesn't openly publish the number, the
rumor is that the 525 actually makes 548 hp.
Don't forget, one of the nicest things about the 525 besides the Vic Jr. alum
heads is that the block is CNC machined, so unlike almost all other 502 based
motors you won't have to add a quart of oil to it everyday!
Another item that I notice that was missing was the "sweeper" style CMI
ss headers on the 525 instead of the "elbow top" style on the old 500's.
Keith Sayre

[Not So Fast]

Lots of good info here. Although Merc doesn't openly publish the number, the
rumor is that the 525 actually makes 548 hp.
Don't forget, one of the nicest things about the 525 besides the Vic Jr. alum
heads is that the block is CNC machined, so unlike almost all other 502 based
motors you won't have to add a quart of oil to it everyday!
Another item that I notice that was missing was the "sweeper" style CMI
ss headers on the 525 instead of the "elbow top" style on the old 500's.
Keith Sayre
Hey, easy on the 500's huh:D Scott told me I would burn oil also but so far not a drop:idea: I change at 20-25 hrs if that helps:D if I had my druthers I would have liked a 525 but the prices are a little prohibitive for retired folk:D NSF

[Keith E. Sayre]

I've seen you out there Bobby, your boat runs great! Frankly, I don't know
how you sleep after I heard what you paid for that HP500!! Good for you!

[Patyacht]

The 1st 525's were set up rich and burned lots of oil and turned many transoms black.. Merc set up a new program for the pcm and now the newer mods are cleaner burning. I've not used any oil in my 07 DCB with 525's. I also change oil every 20-25 hours.

[Kona20]

I assume that both are NA. Is there a Merc 525 thats in factory blown?

[ToMorrow44]

Like someone else mentioned, the new 525s are just more advanced and have a different ignition system. The 525 uses individual coils instead of a distributor and wires. The whipple kit for the 525 is the same as the 500efi so you actually have to change the ignition system and add a distributor, but once that works, then I've heard they make 800+hp with the whipple. Overall its just an updated motor.
The old-school 525s had little b&m blowers with a single carb, but no blown 525s from the factory anymore.
-Tom

[ULTRA26 # 1]

I assume that both are NA. Is there a Merc 525 thats in factory blown?
To answer your question, yes. Merc made a 525SC some years ago that was basically a 454 Mag with a Weiand 250 Blower on it.